Many mathematical models exist for simulation of quantity and quality parameters of receiving waters. Such models are frequently used in the evaluation of effects on receiving waters of pollution control alternatives such as advanced waste treatment and nonpoint source runoff abatement practices. This project has assembled detailed data sets, sufficient for model calibration and verification, for seven sites: Otter Creek, Vermont; Winooski River, Vermont; Chattahoochee River, Georgia; Lower Fox River, Wisconsin; Lake Okeechobee, Florida; Lake Jackson, Florida; Potomac Estuary, Maryland and Virginia. The data are contained in this, on magnetic tape and in addenda. They include physical data (e.g., reach lengths, cross sections), hydrologic and hydraulic data; inflows and outflows, pollutant loads, and in-stream concentrations.